# 4 sided die, rolled twice problem

• Sep 8th 2012, 10:23 PM
Mizen
4 sided die, rolled twice problem
A four-sided die is rolled twice and the scores (1, 2, 3 or 4) recorded on each roll.
(a) What is the sample space for this experiment?
(b) Let X equal the larger of the two outcomes if they are different and the common value if they are the same. Write down the probability table for x.
(c) Find a formula for the probability (mass) function, (p.m.f.), f(x).

I know Part (A).

S = {(1,1),(1,2),(1,3),(1,4),(2,1),(2,2),(2,3),(2,4),( 3,1),(3,2),(3,3),(3,4),(4,1),(4,2),(4,3),(4,4)}

I'm not sure of what there asking for Part (B). Would X be everywhere there is 3 and 4 both when its different [(3,4)?] and when they are same [(3,3) & (4,4)?]?

Part (C) I'm not sure of also but I know it would be some formula including X and the denominator being 16.

Thanks
• Sep 9th 2012, 02:39 AM
Plato
Re: 4 sided die, rolled twice problem
Quote:

Originally Posted by Mizen
A four-sided die is rolled twice and the scores (1, 2, 3 or 4) recorded on each roll.
(a) What is the sample space for this experiment?
(b) Let X equal the larger of the two outcomes if they are different and the common value if they are the same. Write down the probability table for x.
(c) Find a formula for the probability (mass) function, (p.m.f.), f(x).
I know Part (A).
S = {(1,1),(1,2),(1,3),(1,4),(2,1),(2,2),(2,3),(2,4),( 3,1),(3,2),(3,3),(3,4),(4,1),(4,2),(4,3),(4,4)}
I'm not sure of what there asking for Part (B). Would X be everywhere there is 3 and 4 both when its different [(3,4)?] and when they are same [(3,3) & (4,4)?]?
Part (C) I'm not sure of also but I know it would be some formula including X and the denominator being 16.

\$\displaystyle X=1\$ in only one way, \$\displaystyle \{(1,1)\}\$.

But \$\displaystyle X=4\$ happens in each of \$\displaystyle \{(1,4),(2,4),(3,4),(4,1),(4,2),(4,3),(4,4)\}\$ or seven ways.